Disposable absorbent pad

ABSTRACT

An absorbent pad structure is provided of the sort that is arranged to be disposable and that is particularly suited for use in forming disposable diapers. The disclosed structure incorporates pad means of moisture permeable material having a peripheral margin thereof rendered moisture impermeable and a moisture impermeable backing sheet secured at the peripheral margin of the pad means.

United States Patent [1 1 Miller et al.

[i 3,799,167 Mar. 26, 1974 DISPOSABLE ABSORBENT PAD Inventors: Alan H.Miller, Hickory; Grover C.

Currie, Lenoir, both of NC.

Cellu-Products Company, Patterson, N.C

Filed: Dec. 30, 1971 Appl. No.: 214,168

Assignee:

US. Cl. 128/287 References Cited Ruffo 128/287 Grad et a1. 128/290 R Joa128/290 P Mesek et al. 128/287 Jones 128/290 R Primary Examiner-CharlesF. Rosenbaum Attorney, Pinckney Agent, or

F irm-Richards, Shefte &

ABSTRACT An absorbent pad structure is provided of the sort that isarranged to be disposable and that is particularly suited for use informing disposable diapers. The disclosed structure incorporates padmeans of moisture permeable material having a peripheral margin thereofrendered moisture impermeable and a moisture impermeable backing sheetsecured at the peripheral margin 2 Drawing Figures 5 UNITED STATESPATENTS 1,850,033 3/1932 Ritter 128/290 R ofthe pad means 2,005,2986/1935 OBrien 8! a] 128/290 R 3,059,644 10/1962 Atkinson 128/290'R 1Claim,

I 1" 54 f \'r- .fi

DISPOSABLE ABSORBENT PAD BACKGROUND OF THE INVENTION Disposable diapersas heretofore developed in the art commonly employ an absorbent pad ofplied and creped wood pulp wadding covered with a moisture permeablenon-woven fabric sheet and backed by a moisture impermeable protectivesheet. Representative prior disclosures are found in US. Pats. No.2,788,003, Reissue No. 26,151, and No. 3,426,756. A problem evident fromthese prior disclosures has been that of providing satisfactorilyagainst leakage of waste materials by wicking or seepage at the edges ofthe diaper. The present invention deals effectively with this problem inan improved manner.

SUMMARY OF THE INVENTION Briefly described, the present invention ischaracterized by the combination of pad means of moisture permeablematerial having a peripheral margin thereof rendered moistureimpermeable and a moisture impermeable backing sheet secured to the padmeans at its peripheral margin so as to be sealed thereat againstlateral escape of moisture from the pad means.

The peripheral margin of the pad means is rendered moisture impermeableby treatment with a suitable waterproofing composition as noted furtherbelow, and marginal sealing of the backing sheet is preferablyeffected'with a waterproof adhesive, although heat sealing may beemployed alternatively for this purpose if desired.

DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a disposable diaperstructure embodying the present invention; and

FIG. 2 is an enlarged partial section detail taken substantially at theline 22 in FIG. 1.

DETAILED DESCRIPTION OFTHIS INVENTION The disposable diaper structureillustrated in the drawings, and indicated generally by the referencenumeral It), incorporates a pad means 12 formed by a core pad 14 ofabsorbent material, such as plied and creped wood pulp wadding of theusual sort, with a covering sheet 16 of moisture permeable non-wovenfabric of hydrophobic character, such as may be formed with blendedacrylic and rayon fiber, applied thereto.

As shown, the diaper structure is shaped rectangularly in plan with thenon-woven cover sheet 16 extending somewhat beyond the core pad 14 inboth length and breadth. For example, in a diaper size using a core pad14 in a length of 16 inches and a width of 12 inches, the dimension ofcover sheet 16 should be increased by I inch in both directions so as toprovide a r inch extension all around for the securing purposesexplained in detail further below.

Additionally, a peripheral margin of the pad means 12 is renderedmoisture impermeable by treating the cover sheet 16 with a waterproofingcomposition in an extent reaching inwardly over the edges of core pad 14as indicated by stipling at 16 in FIGS. 1 and 2. For exemplarydimensions such as are mentioned above, this inward extent of theperipheral waterproofing of cover sheet 16 should reach over core pad 14for about I inch from its edges.

The diaper structure 10 is completed by a waterproof backing sheet 18 ofa moisture impermeable material such as polyethylene film, which isprovided in a size corresponding with that of cover sheet 16 and issecured marginally to cover sheet 16 with a waterproof adhesive, asindicated in FIG. 2 at 20, as as to form a seal thereat against lateralescape of moisture from the core pad 14.

The result of this arrangement is to contain the abosrbent core pad 14edgewise within a moisture impermeable envelope that not only eliminatesall problem with leakage of waste materials therefrom, but also preventsany objectionable separation of core pad portions from the pad unitduring use, which has been a further problem with prior artarrangements.

Treatment of the covering sheet 16 to render its peripheral margin 16'moisture impermeable can be effected with any composition that willapply readily to saturate the covering sheet material and cure towaterproof the same without stiffening unduly or being chemicallyirritating in any respect during use of the pad unit. A suitablecomposition meeting these requirements employs (by weight) parts ofemulsified acrylic polyester at 40-70 percent solids formulated withl-l5 parts of emulsified polyacrylic acid salt at 20-40 percent solidsand adjusted for proper application viscosity with 3-12 parts of avolatile amine or hydroxide base as well as incorporating 0.1-5.0 partsof a latent acid catlyst.

Alternatively, a solvent solution of 100 parts (by weight) of acrylicpolyester at 40-70 percent solids with 15-45 parts of formaldehyde, ureaor melamine type resins at 50-90 percent solids may be used. Either ofthese compositions can be applied effectively to nonwoven covering sheetmaterial by roller printing and cured in times ranging from 15 secondsto 5 minutes at temperatures within the range of 200 to 450F.

A further composition that may be used is composed of I00 parts (byweight) of emulsified and stabilized butyl'rubber polymer at 40-70percent solids which may be cured with or without heat (up to 350F) infrom 20 minutes to overnight, or from which vulcanilates may be obtainedby adding 2-6 parts of elemental sulfur or 2-l0 parts of zinc diethyldithiocarbamate or 2-8 parts of zinc dibutyl dithiocarbamate, togetherwith a small amount of soluble ionic dithiocarbamate or 2-5 parts of analkaline dispersion of guanadine acetate. Such additions are mixed withthe butyl rubber polymer at a pH of 7.0-9.5, and viscosity is adjustedby further addition of l-8 parts of ammonium or sodium carboxymethylcellulose or 0.1-3.0 parts of ammonium or sodium chloride. Whenevernecessary application tack may be improved by the further addition of5-30 parts phenol-formaldehyde resin or the like.

Any of these formulations may be pigmented if desired although the firstand last ones require use of a primary dispersant for this purpose.Also, all three formulations can be modified to exhibit fire retardantproperties by the addition of 15-45 parts of zinc b0- rate, aluminatrihydrate, or alumina hexahydrate.

In addition, either of the first two formulations can be used quite wellas adhesives for securing the covering and backing sheets 16 and I8peripherally when adjusted to a suitably increased viscosity for thispurpose.

The procedure for forming a pad structure 10 in accordance with thepresent invention for disposable diaper use follows usual practice inplying and creping (or embossing) the wood pulp wadding and then cuttingthe same transversely to form successive core pads 14 of proper size.Then the cut core pads 14 are laminated in registering relation betweena suitably wider top running stip of the non-woven covering sheetmaterial, to which a formulation of the foregoing sort has been appliedand cured to render the same moisture impermeable at the areas that willform the peripheral margins 16' in successive pad units 10, and acorrespondingly wide bottom running strip of the moisture impermeablebacking sheet material, to which securing adhesive has been applied toform the peripheral seal 20 during the laminating step. After which, thelaminated structure, still in running strip form, is box pleated to theusual disposable diaper disposition and then cut into separate diaperunits and finally doubled lengthwise to the arrangement in which suchunits are normally packed for marketing.

The present invention has been described in detail above for purposes ofillustration only and is not intended to be limited by this descriptionor otherwise to exclude any variation or equivalent form or procedurethat would be apparent from, or reasonably suggested by, the foregoingdisclosure to the skill of the art.

We claim:

1. A disposable absorbent pad comprising a moisture impermeable backingsheet, a core pad of abosrbent material superimposed on said backingsheet, and a moisture impermeable covering sheet applied to said corepad, said backing and covering sheets corresponding in size andextending peripherally beyond said core pad, and said covering sheetbeing treated to render the same moisture impermeable at a continuousperipheral margin thereof reaching inwardly over a substantialperipheral portion of said core pad and being secured to said back sheetthroughout the entire peripheral extent of said margin so as to form aseal thereat against lateral escape of moisture from said core pad inany direc- PO-ww UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent N 3.799.167 Da d March 26. 1974 I r) Alan H. Miller and Grover C.Currie It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Column 2, line 4, after "20" delete "as" and insert therefor -so; Column2, line 8, delete "abosrbent" and insert therefor -absorbent; Column 2,line 27, delete "catlyst" and insert therefor -catalyst; Column 2, line48, delete "ammonium" and insert therefor --methyl-; Column 3, l ine 3,delete "stip" and insert therefor -st rip; Column 4, line 8, delete"impermeable" and insert therefor permeable;i Column 4, line 15, delete"bask" and insert therefor -backing-.

Signed and sealed this 4th day'of-February 1975.

(SEAL) Attest:

McCOY M. GIBSON JR. c. MARssALL DANN Attesting Officer Commissioner ofPatents

1. A disposable absorbent pad comprising a moisture impermeable backingsheet, a core pad of abosrbent material superimposed on said backingsheet, and a moisture impermeable covering sheet applied to said corepad, said backing and covering sheets corresponding in size andextending peripherally beyond said core pad, and said covering sheetbeing treated to render the same moisture impermeable at a continuousperipheral margin thereof reaching inwardly over a substantialperipheral portion of said core pad and being secured to said back sheetthroughout the entire peripheral extent of said margin so as to form aseal thereat against lateral escape of moisture from said core pad inany direction.